1. Technical Field
Novel photoresist monomers, polymers thereof and photoresist compositions containing the same are disclosed. In particular, photoresist monomers are disclosed which are suitable for a photolithography process using DUV (deep ultraviolet) light sources, particularly VUV (vacuum ultraviolet: 157 nm) in fabricating a minute circuit for a high integration semiconductor device, photoresist polymers thereof and photoresist compositions containing the same, and preparation processes are also disclosed.
2. Description of the Related Art
In general, a useful photoresist for ArF and VUV has a variety of desired characteristics, such as low light absorbance at the wavelength of 193 nm and 157 nm, excellent etching resistance, and excellent adhesiveness to a wafer. In addition, a photoresist should be easily developable in a commercially readily available developing solution, such as 2.38 wt % and 2.6 wt % aqueous tetramethylammonium hydroxide (TMAH) solution.
Recently, much research has been conducted on resins having a high transparency at the wavelength of 248 nm and 193 nm and dry etching resistance similar to novolac resin. However, most of the photoresists are not suitable for VUV due to their poor transmittance at 157 nm wavelength.
Research on polyethylene or polyacrylate containing fluorine has also been conducted. Unfortunately, most photoresists containing fluorine with a polyethylene, polystyrene or polyacrylate polymer backbone have weak etching resistance, low solubility in an aqueous TMAH solution and poor adhesiveness to the silicon wafer. In addition, these photoresists are difficult to mass-produce and are expensive.
On the other hand, photoresists containing fluorine with alicyclic polymer or maleicanhydride-norbonene polymer backbone have good adhesiveness to the silicon wafer, low light absorbance at the wavelength of 157 nm and excellent etching resistance compared to photoresists with polyacrylate backbone.
Besides the above photoresist containing a photoresist polymer, which is prepared by using butadiene sulfone instead of maleicanhydride as a comonomer, has a low light absorbance at the wavelength of 157 nm and an excellent etching resistance.